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From: Scrim on 5 Apr 2010 12:49
Is there a DIY circuit out there for a good current tracer? I have a
valuable multilayer pcb with a short between a power supply line and earth I
can't find. The basic idea is to inject a string of pulses through shorted
circuit and use a small solenoid type sensor to follow the current path
until the short is reached.

Thanks,

Alan

From: Arfa Daily on 5 Apr 2010 13:10

"Scrim" <nospam(a)nospam.nospam> wrote in message
news:1woun.157498$1j3.78945(a)newsfe10.ams2...
> Is there a DIY circuit out there for a good current tracer? I have a
> valuable multilayer pcb with a short between a power supply line and earth
> I can't find. The basic idea is to inject a string of pulses through
> shorted circuit and use a small solenoid type sensor to follow the current
> path until the short is reached.
>
> Thanks,
>
> Alan

Sometimes, a low ohms meter such as the Bob Parker ESR meter, can be a
valuable aid to finding PCB shorts. Also, allowing a limited non-damaging
current to flow round the PCB and through the short, can cause a rise in
track temperatures, that can be seen in the dark, with a reasonably
sensitive CCD camera.

Arfa


From: tm on 5 Apr 2010 14:17

"Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message
news:rQoun.195146$ti6.157619(a)newsfe24.ams2...
>
> "Scrim" <nospam(a)nospam.nospam> wrote in message
> news:1woun.157498$1j3.78945(a)newsfe10.ams2...
>> Is there a DIY circuit out there for a good current tracer? I have a
>> valuable multilayer pcb with a short between a power supply line and
>> earth I can't find. The basic idea is to inject a string of pulses
>> through shorted circuit and use a small solenoid type sensor to follow
>> the current path until the short is reached.
>>
>> Thanks,
>>
>> Alan
>
> Sometimes, a low ohms meter such as the Bob Parker ESR meter, can be a
> valuable aid to finding PCB shorts. Also, allowing a limited non-damaging
> current to flow round the PCB and through the short, can cause a rise in
> track temperatures, that can be seen in the dark, with a reasonably
> sensitive CCD camera.
>
> Arfa
>

Stick the board in the freezer. When you remove it and apply current limited
power
to the suspected circuit, the frost will melt showing just where the short
is.



From: stratus46 on 5 Apr 2010 17:13
On Apr 5, 9:49 am, "Scrim" <nos...(a)nospam.nospam> wrote:
> Is there a DIY circuit out there for a good current tracer? I have
a
> valuable multilayer pcb with a short between a power supply line
and earth I
> can't find. The basic idea is to inject a string of pulses through
shorted
> circuit and use a small solenoid type sensor to follow the current
path
> until the short is reached.
>
> Thanks,
>
> Alan

Has it ever worked or is this a failure? Are you thinking incomplete
etch or shorted bypass cap?

G²
From: Doug White on 5 Apr 2010 17:37
"tm" <noone(a)msc.com> wrote in news:hpd96c$71g$1(a)speranza.aioe.org:

>
> "Arfa Daily" <arfa.daily(a)ntlworld.com> wrote in message
> news:rQoun.195146$ti6.157619(a)newsfe24.ams2...
>>
>> "Scrim" <nospam(a)nospam.nospam> wrote in message
>> news:1woun.157498$1j3.78945(a)newsfe10.ams2...
>>> Is there a DIY circuit out there for a good current tracer? I have a
>>> valuable multilayer pcb with a short between a power supply line and
>>> earth I can't find. The basic idea is to inject a string of pulses
>>> through shorted circuit and use a small solenoid type sensor to
>>> follow the current path until the short is reached.
>>>
>>> Thanks,
>>>
>>> Alan
>>
>> Sometimes, a low ohms meter such as the Bob Parker ESR meter, can be
>> a valuable aid to finding PCB shorts. Also, allowing a limited
>> non-damaging current to flow round the PCB and through the short, can
>> cause a rise in track temperatures, that can be seen in the dark,
>> with a reasonably sensitive CCD camera.
>>
>> Arfa
>>
>
> Stick the board in the freezer. When you remove it and apply current
> limited power
> to the suspected circuit, the frost will melt showing just where the
> short is.

Spray freeze is faster, or if you have a can of freon "duster" around,
turn it upside down (it's the same stuff). Hose down the suspected area,
turn on a current limited supply across the short, and Voila!

Doug White
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